Purchasing the correct hardware: dual-core intel? Big cache?

[Martin Hepworth]

Bill

if the database is CPU dependant I'd look at tuning the queries/indexes and
that stuff...it really shouldn't be CPU bound.

--
martin

On 4/24/06, Bill Moran <wmoran at potentialtech.com> wrote:
>
> On Mon, 24 Apr 2006 23:03:59 +0100
> "Martin Hepworth" <maxsec at gmail.com> wrote:
>
> > Bill
> >
> > depends on the application itself, but more RAM and the disk layout
> (RAID)
> > will be more important than the CPU. Also depends on how write-heavy the
> > apps are...
>
> Thanks for the feedback, Martin.
>
> I'm fully aware of the app-dependency - what I'm looking for is a way
> to test the application.  I've got 3 different clusters available for
> testing, but I'm not sure how to tell if the cache is getting used
> heavily or not.
>
> I've already determined that the database server is CPU-bound under
> our test load.  With high-speed SCSI disks and battery-backed RAID,
> there's not enough IO to stress the disk subsystem.  RAM is almost a
> non-issue.  With the machine stressed at full load, it's only using
> 1/8 of the available RAM.
>
> So, my current bottleneck is CPU power.  And the boss has asked me
> for the best way to overcome this bottleneck.  We're looking at either
> the same CPUs we already have, but with _huge_ caches (8m) - or going
> with more CPUs by getting true dual-core pentiums.
>
> The question this all pivots on is will 8M of cache be a significant
> improvement?  If not, then we're going with the dual-core CPUs.  What
> I'd like is some way to take an existing system and determine how often
> the cache is getting invalidated, so I can make some guesstemate as to
> whether more cache will help or not.
>
> >
> > --
> > martin
> >
> > On 4/24/06, Bill Moran <wmoran at potentialtech.com> wrote:
> > >
> > >
> > > I've been asked to make some hardware recommendations, I'm hoping some
> > > folks on the list can make some suggestions.
> > >
> > > We're looking hard at getting either Intel dual-core procs, or getting
> > > hyperthreaded procs with huge (8M) caches.
> > >
> > > We currently have a few dual proc Intel HT machines that we can test
> > > out our workload on, and I'm trying to get a feel for how to determine
> > > if a larger cache size will generate better performance than replacing
> > > HT procs with full-blown dual-core procs.  We're looking at the 6850
> > > from Dell, which supports both processor families:
> > >
> > >
> http://www1.us.dell.com/content/products/productdetails.aspx/pedge_6850?c=us&cs=555&l=en&s=biz
> > >
> > > The goal for these machines is to serve out PosgreSQL databases to as
> > > many Apache+php front ends as we can hang off each one.  So we're
> trying
> > > to purchase hardware that will create a DB server that can handle a
> lot
> > > of web server front ends.
> > >
> > > I have a Dell 2850 (dual HT procs) here that I can use for testing.
> > > I'm a little fuzzy on determining how well the cache is working, so
> I'm
> > > stuck on whether or not the 8M cache that's available on the HT units
> > > is worth the money or not.  Can anyone suggest a testing methodology
> > > that will isolate this particular aspect?
> > >
> > > --
> > > Bill Moran
> > > Collaborative Fusion Inc.
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>
> --
> Bill Moran
> Collaborative Fusion Inc.
>
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